Nature - USA (2020-01-16)

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nature research

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life sciences reporting summary

November 201

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6. Statistical parameters
   For all figures and tables that use statistical methods, confirm that the following items are present in relevant figure legends (or in the
   Methods section if additional space is needed).

n/a Confirmed

The exact sample size (n) for each experimental group/condition, given as a discrete number and unit of measurement (animals, litters,

cultures, etc.)

A description of how samples were collected, noting whether measurements were taken from distinct samples or whether the same

sample was measured repeatedly

A statement indicating how many times each experiment was replicated

The statistical test(s) used and whether they are one- or two-sided

Only common tests should be described solely by name; describe more complex techniques in the Methods section.

A description of any assumptions or corrections, such as an adjustment for multiple comparisons

Test values indicating whether an effect is present

Provide confidence intervals or give results of significance tests (e.g. P values) as exact values whenever appropriate and with effect sizes noted.

A clear description of statistics including central tendency (e.g. median, mean) and variation (e.g. standard deviation, interquartile range)

Clearly defined error bars in all relevant figure captions (with explicit mention of central tendency and variation)

See the web collection on statistics for biologists for further resources and guidance.

ü Software

Policy information aboutavailability of computer code

7. Software
   Describe the software used to analyze the data in this
   study.

For manuscripts utilizing custom algorithms or software that are central to the paper but not yet described in the published literature, software mustbemade

available to editors and reviewers upon request. We strongly encourage code deposition in a community repository (e.g. GitHub).Nature Methodsguidance for

providing algorithms and software for publicationprovides further information on this topic.

ü Materials and reagents

Policy information aboutavailability of materials

8. Materials availability
   Indicate whether there are restrictions on availability of
   unique materials or if these materials are only available
   for distribution by a third party.

Quantitation of immunohistochemistry images was performed using NIS Elements v4.50

(Nikon Instruments). Quantitation of histological images of fibrosis was performed using

Adobe Photoshop CS5. Analysis of echocardiographic data was performed using VevoLAB

v1.7.1. (VisualSonics). Analysis of analytical flow cytometry data was performed using FlowJo

V.10 (Tree Star, Inc). Acquisition of passive tissue force measurements was performed using

DMC v600A (Aurora Scientific). For statistical analysis, two-tailed t-tests (Figures 4d, 4e) were

performed using Microsoft Excel, Office365 version. All other tests, including one-way

analysis of variance (ANOVA), survival curve analysis, and normality tests, were performed

usingGraphPadPrismversion8.0.1.

Kit-MerCreMer x R-GFP mice used for lineage tracing will be made available under a materials

transfer agreement (MTA) between the requesting institution and Cincinnati Children's

Hospital. All other materials and reagents were obtained from commercial sources (see

Online Methods for full description).